The invention is based on a method for producing a throttle in a flow channel of a component, in particular a valve part. The invention is further based on an apparatus for implementing the method.
In valves which are used in automotive engineering, and there, in particular, in fuel injection technology, a flow channel, which runs within a valve part of a fuel injector, serves to control a pressurized medium flowing through the flow channel extending between a control chamber of a guide bore, in which an injection valve member is accommodated, and a valve seat of the valve part. In order to obtain a stable flow through the valve, and hence a precisely defined, controllable injection behavior, even in the event of low pressure in the control chamber, the flow cross section in the flow channel is purposefully constricted by means of a throttle configured in the inflow-side inlet region of the flow channel, which throttle is also referred to as an outlet throttle.
A method for stamping, decorating and shaping a semifinished product is known from DE 25 01 465. The semifinished product is here shaped by means of a forming tool, while the stamping is performed by means of an appropriately configured counter-die. Alternatively, if a negative forming tool is used, the stamping is performed by means of a stamping die. A drawback herewith is that this method is suitable only for the stamping of foils on a carrier material and thus has only a limited range of application.
In traditional, known valves, in particular of the kind for use in fuel injection systems, the outlet throttle extending between the control chamber and a funnel of the valve, said funnel being configured as a closing element, is produced, for instance, by a stamping process and a following erosion process, whereby the throttle geometry is produced. If the respective process axes of both processes do not here run coaxially to each other, but rather the two process-determining axes, due to a misorientation for instance, are mutually offset, in that the erosion operation, for example, has an eccentricity in relation to the stamping operation, then a discrepancy arises between the stamping geometry and the erosion geometry in the throttle which is hereupon produced, whereby the effective length of the throttle is influenced or shortened and thus the flow characteristics of the throttle in the valve part are influenced. This can lead to increased risk of cavitation in the throttle which is produced in this way. The flow through a throttle which does not reliably produce cavitation would react to different differential pressures before and after the throttle with changes in volumetric flow rate, which makes quantity control more difficult. In addition, it can happen that, in the stamping operation, a herein occurring axially offset residual cross section of the throttle contour, i.e. the narrowest cross section which remains open after the stamping operation, cannot be fully removed by the erosion operation. Together with the erosion contour, an over-large cross section for the medium which flows through during normal operation of the valve part can thereby be obtained.